DESCRIPTION: This study will examine the role of stress, distress and bruxism in pain exacerbation in myofascial TMD. It will also evaluate the role of bruxism in moderating the efficacy of a commonly used oral appliance. The study will recruit 85 new admissions to the TMD clinic at the Univ. of Medicine and Dentistry of New Jersey (UMDNJ) who meet diagnostic criteria for myofascial TMD and who have had no prior treatment with oral appliances for facial pain. A group of 85 control subjects without any TMD will also be recruited from the non-TMD clinics at UMDNJ. To test the role of stress, distress, and bruxism in exacerbating facial pain, TMD patients and controls will complete daily diaries of stress, distress and pain for one week. At beginning of this period and exactly one week later, full-mouth dental impressions will be taken. These impressions will be used to prepare micrographs that will be examined under a scanning electron microscope. By examining changes in scratch marks between the two periods, subjects will be graded for severity of bruxism. Regression models will test the relation between stress, distress, bruxism, and facial pain. Analyses will also compare severity in bruxism in TMD patients and controls. To test the role of bruxism in treatment outcome, TMD patients will then be randomly assigned to receive either a full-coverage hard acrylic splint or palatal splint. In two followup visits over the following month, pain and disability will be assessed. Analyses will examine whether the efficacy of the active vs. palatal splint is moderated by the degree to which patients show evidence of bruxism.